The Spanish fashion retail giant Zara has apologised to ultra-orthodox Jews in Israel for selling men's suits that violate a religious prohibition against mixing wool and linen, a company spokesman confirmed today. It has withdrawn the offending garments from its racks.

Jewish law prohibits the wearing of wool-and-linen blends, known as "shatnez", and the ultra-orthodox carefully inspect materials of unknown fibres. Some rabbis link the taboo to garments worn by idol-worshipers and to the biblical sacrifices of Cain (flax) and Abel (sheep).

About 40 or 50 Israeli clients complained about the shatnez suits. The conservatively dressed orthodox Jews are not a mainstay of the popular Zara shops in Israel, but as the Jerusalem Post pointed out, they do manage to find classic cuts amid the low necklines and high hems.

"Zara's client base is so broad that we don't want to leave anybody out, much less insult anybody," a spokesman at Zara headquarters in north-west Spain told the Guardian.

Zara is the leading fashion retail chain in Israel, with 15 stores, 900 employees and $340m in annual sales.

The company placed advertisements in ultra-orthodox media to apologise for what it said was a production error. "Zara regrets its mistake and assures its clients in Israel, particularly its orthodox clients, that it will do everything in its power to make sure the mistake is not repeated," the statements read.

The company has also offered to pay for the cost of removing the blend and will refund clients for rigorous shatnez inspections, required of almost every article of clothing, according to the Shatnez Testers of America. According to the association's website, shatnez is most often detected in the collar of men's jackets, where linen canvas is used to give the collar shape. The website explains the procedure "to make the garment kosher".